


Costume Party

by U_know_u_luv_me_99



Category: Mortal Instruments Series - Cassandra Clare
Genre: Costumes, Halloween, M/M, Smut, but still, i might continue this, it's a bit early but whatever, really badly written smut
Language: English
Status: Completed
Published: 2015-10-08
Updated: 2015-10-17
Packaged: 2018-04-25 11:31:16
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 1,680
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4958965
Author URL: https://archiveofourown.org/users/U_know_u_luv_me_99/pseuds/U_know_u_luv_me_99
Summary: <blockquote class="userstuff">
              <p>Alec really didn't think he was going to dress up for Halloween, but somehow it ended up happening anyway. At least Magnus was please.</p>
            </blockquote>





	1. Chapter 1

Alec had never liked Halloween. It was a mundane tradition that Jace and Izzy had loved, both of them using it as a chance to dress up as sexy policemen, or sexy cats, or the particularly memorable sexy teddy bears. Max always used it as a chance to dress up as his favourite anime characters, and Alec would take him trick or treating, but he never dressed up. He should have known that wouldn't last once he started dating Magnus.

 "Please!" Magnus said, although it was really more of a whine. They were standing in Alec's bedroom, talking about Halloween.

"No!" Alec insisted, crossing his arms over his chest and glaring at his boyfriend.

"But you'll look so cute!" Magnus continued.

"I'm not dressing up." Magnus pouted. 

"Fine. But you'll at least come to the party right? It's going to be fabulous. I mean, of course it is, it's mine. But still, this one looks like it should be particularly good."

"Yes, I'm coming," Alec said, a small smile appearing on his face. "I wouldn't miss it for the world." He wrapped his arms around the warlock's neck, pulling him down for a quick kiss. Magnus hummed and tried to deepen it but Alec pulled away. "Uh-uh," he said, shaking his head with a sneaky smile. Magnus pouted but pulled away. Just then, Alec's door swung open and Izzy skipped in. Alec sighed.

"Alec, you and I have to talk costumes," she said. Alec growled, and Magnus laughed.

"I'll be going. I've got a party to set up after all." He pecked Alec on the lips once more, and flounced his way out of the room.

Alec turned to his sister. "I'm not wearing a costume."

"Oh, yes you are." She said, a sly grin on her face. "Imagine the look on Magnus's face when you turn up as a sexy vampire."

"There's no way I'm dressing up as a vampire, sexy or not. And I already told Magnus I wasn't dressing up," Alec said, sitting down on his bed.

"Even more reason to dress up. It would be a nice surprise," she insisted, sitting beside him.

Alec knew that resistance was futile. He could usually get Magnus to give in, but his siblings were a different matter. And if he was being completely honest, he kind of wanted to dress up. He wasn't going to tell anyone that, obviously, but he might be willing to be persuaded.

"What did you have in mind?" he asked. Izzy squealed and clapped her hands excitedly. 

"I honestly didn't think you were going to give in that easily." Alec just shrugged.

"You weren't exactly going to let up," he said. Izzy grinned, and Alec started to regret it.

"So, I was thinking sexy doctor," she began, and Alec instantly shook his head. 

"Nothing sexy, just give me a normal costume." Izzy groaned, but stood up to look through Alec's closet.

"Well you've got nothing in here unless you want to be a dull goth, so Jace's room it is." She grabbed his hand and dragged him into Jace's room. Jace was sitting at his desk, and he looked up when they came in. "Alec needs a costume," she stated, and a menacing grin appeared on his face. "He said nothing sexy." Jace's smile fell. He pouted, but stood up and looked through his closet anyway. He laughed suddenly, and pulled something out of the closet, showing it to his siblings. Izzy squealed again, and Alec looked at it carefully, before nodding reluctantly. He was definitely going to regret this.

 

Magnus's party had been in full swing for half an hour now, and he still couldn't see Alec. He stood waiting by his door, pretending to be observing the crowd so that he didn't look too pathetic. He didn't think he was successful. The front door opened, and he saw Jace and Izzy walk in, dragging a reluctant Clary and Simon behind them. All four were dressed up, Izzy as a sexy firefighter, Jace as a sexy soldier, Clary as some sort of fairy thing, and Simon as Jon Snow, although it wasn't a very good costume. Magnus frowned when he didn't see Alec, but Izzy caught his eye and winked. His frown deepened. Izzy's winks were rarely a good sign.

The door opened again, and Magnus looked back. He froze when he saw Alec. Alec was dressed up as a cheerleader. Not a sexy cheerleader, not a female cheerleader, just a normal cheerleading outfit. It was the hottest thing Magnus had ever seen. He rushed to Alec, grabbing his shoulders and holding him at arms length, looking him up and down. "I thought you weren't going to dress up," he said.

"I changed my mind," Alec replied. "Do you like it?"

"Are you kidding?" Magnus gasped. "I love it. You look fabulous."

"As do you," Alec said. Magnus twirled, the coat from his pirate costume spinning around. 

"We make quite the pair. Me, plundering ships, you cheering me on. We'd take over the world."

"Of course we would," Alec said. "Although, if you wanted me to cheer for you, you just had to ask. I'm always up for a good plundering." Alec really didn't think that made any sense, but it seemed to have the desired affect as Magnus began to pull him towards their bedroom.

 


	2. Chapter 2

**Notes for the Chapter:**

> Sorry, I'm kind of new to smut, so this is probably dreadful.

Magnus pulled Alec into their bedroom. As soon as the door closed behind them, Alec pulled the warlock down, kissing him passionately. “What made you decide to dress up?” Magnus asked after he managed to tear himself away. “And where did you get that costume?”

“It’s Jace’s,” Alec said, and Magnus pouted, “And I decided to dress up, so that I could see the look on your face when I did.”

“You’re gorgeous,” Magnus said, kissing Alec again. “Is this going to be a regular thing? Because if it is, I have some great ideas for couple’s costumes.” Alec laughed, but didn’t answer. Instead, he pulled the older man towards the bed, falling back on it. Magnus smirked and crawled on top of him.

“You gonna get started?” Alec asked, but he gasped when Magnus began to suck at his neck. The warlock’s hands were running up and down Alec’s sides, pulling at the material of his costume.

“You look so hot,” he gasped out, and Alec flushed. “But next time, you should totally wear a skirt.” Alec’s face was as red as it could be, but his voice was strong when he replied.

“Aye aye, Captain.” Magnus laughed, before pushing Alec’s shirt up to his neck. He leant down and began to mouth at Alec’s nipples. Alec moaned and brought one of his hands up to tweak the nipple that wasn’t getting Magnus’s attention. Magnus’s hands moved down to the shadowhunter’s hips, pushing his pants down.

“Magnus,” Alec gasped as Magnus began to stroke his dick. Magnus lifted up, looking down at Alec’s eyes, a vicious smile on his face.

“I want to hear you scream,” he said, and Alec couldn’t help the loud moan that he let out. Magnus laughed, before leaning down and replacing his hand with his mouth. Alec’s hand flew to Magnus’s hair as his boyfriend swallowed him down.

Alec began to lose control. His moans became louder, and he pulled Magnus’s head down, hips thrusting up. Magnus always made him crazy. Alec had no experience outside of Magnus, but he was pretty sure Magnus was fucking amazing.

Alec’s head felt fuzzy, and he did scream when he felt Magnus’s finger pushing at his hole. The finger pressed in slightly, but didn’t go far. “Please!” Alec begged. “Please, Magnus, I need it.” Magnus pulled away, and Alec nearly cried with frustration.

“Shhh, I’m just getting the lube,” Magnus reassured him. He returned soon, bottle in hand. Alec couldn’t really focus on much, but he gasped when the finger returned, cold and wet. He groaned loudly, arching off the bed as Magnus pressed in.

Magnus prepped him quickly, not wasting time on the foreplay. They were both too far gone to waste time. When Magnus thought Alec was ready, he pulled his fingers out, reaching off the bed for a condom. He slid it on and began to push in.

Tears began to slide down Alec’s face. It felt so good. He still wasn’t used to sex, and the pleasure was almost excruciating when Magnus rubbed against his prostate. Alec screamed, and Magnus grinned down at him. “That’s it,” he said. “Make sure everyone downstairs can hear you.”

The thought made Alec shudder with pleasure. His siblings were downstairs, Jace, Izzy, even Max. He knew they couldn’t hear him, Magnus would never let that happen, but the thought was almost enough to make him cum.

Magnus continued thrusting, hips pounding faster and faster, each thrust hitting that spot inside of Alec. They were both panting and Magnus could tell that he was about to cum. He began to stroke Alec. A few streaks later, Alec was cumming, screaming loudly. Magnus was close behind, body tensing as he came.

He flopped next to Alec, both boys panting heavily. Alec curled into him, resting his head on his chest. “We should go back downstairs,” Magnus said tiredly, and Alec groaned. They both stood up, fixing their costumes which had never fully been removed. Alec attempted to smooth down his hair, and Magnus cleaned the cum off his costume with a sweep of his hand. Alec glared at his immaculate boyfriend and Magnus laughed as they headed downstairs to the rest of the party.

Alec left Magnus to talk to his guests as he sought out his siblings. He found Jace, Clary, Izzy, Simon, and Max standing near the bar, and he quickly checked that no one had given Max alcohol.

“Soooo…” Izzy said. Alec blushed and quickly grabbed a drink from the bar to distract himself.

“Keep the costume, dude,” Jace said. Alec’s blush deepened, but he hid a smirk behind the glass. He was going to have a lot of fun with this outfit.

 

**Author's Note:**

> Check me out on [tumblr](http://u-know-u-luv-me.tumblr.com/), and check my [writing](http://madoulgeris.weebly.com/) [blogs](http://fairytalesoftheworld.weebly.com/).


End file.
